For storage apparatuses, the Redundant Array of Inexpensive Disks (RAID) techniques is used to assure performance and fault resistance by distributing data into a plurality of hard disks (magnetic disk apparatuses). Storage apparatuses realize the RAID techniques which includes data allocation to the disks and making data redundant (multiplexing), and so on, using the RAID controller.
There are recovery techniques called rebuild with which, when a disk belonging to a RAID group fails, data on the failed disk are restored using redundancy of data that have been made redundant. Such recovery techniques include, for example, the techniques described below.
As the first technique, there is the following technique (for example, Patent document 1). A load measuring means measures the busy rates of respective disk apparatuses. The load control means commands the start and stop of the recovering process according to the busy rates. A recovering process means stops the recovering process when the frequency of usage of the recovery source or the recovery destination by the host apparatus is high, and resumes the recovering process when the frequency of accesses from the host apparatuses falls below a certain frequency. As a result, it becomes possible to perform the recovering process without making the input/output (I/O) speed of the host decrease.
As a second technique, there is the following technique (for example, Patent document 2). In a disk array apparatus equipped with two types of parity data and a plurality of data recovery systems, in the case of a failure of a single magnetic disk, a data recovery system with which a degenerated magnetic disk and a magnetic disk with the maximum load may be excluded from the use in the data recovering process is selected. Accordingly, when a failure occurs in a magnetic disk on the disk array apparatus, it becomes possible to reduce delay in the data recovering process due to access load on other magnetic disks.
As the third technique, there is a technique (for example, Patent document 3) in which, in a disk array apparatus with 2-parity configuration, the parity used and data of the recovery source are rotated at the time of read in the case of a correction for failure of one HDD.
Patent document 1: Japanese Laid-open Patent Publication No. 2000-276305
Patent document 2: Japanese Laid-open Patent Publication No. 2005-38271
Patent document 3: Japanese Laid-open Patent Publication No. 2006-260446